U.S. patent number 6,237,606 [Application Number 09/267,756] was granted by the patent office on 2001-05-29 for method of applying energy to tissue with expandable ligator catheter having multiple electrode leads.
This patent grant is currently assigned to VNUS Medical Technologies, Inc.. Invention is credited to Brian E. Farley, Christopher S. Jones, Mark P. Parker, Douglas M. Petty, Joseph M. Tartaglia, Arthur W. Zikorus.
United States Patent |
6,237,606 |
Zikorus , et al. |
May 29, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Method of applying energy to tissue with expandable ligator
catheter having multiple electrode leads
Abstract
A catheter includes a plurality of primary leads to deliver
energy for ligating a hollow anatomical structure. Each of the
primary leads includes an electrode located at the working end of
the catheter. Separation is maintained between the primary leads
such that each primary lead can individually receive power of
selected polarity. The primary leads are constructed to expand
outwardly to place the electrodes into apposition with an
anatomical structure. High frequency energy can be applied from the
leads to create a heating effect in the surrounding tissue of the
anatomical structure. The diameter of the hollow anatomical
structure is reduced by the heating effect, and the electrodes of
the primary leads are moved closer to one another. Where the hollow
anatomical structure is a vein, energy is applied until the
diameter of the vein is reduced to the point where the vein is
occluded. In one embodiment, a secondary lead is surrounded by the
primary leads, and extends beyond the primary leads. The secondary
lead includes an electrode at the working end of the catheter. The
secondary lead can have a polarity opposite to the polarity of the
primary leads in a bipolar configuration. The polarity of the leads
can be switched and the catheter can be moved during treatment to
ligate an extended length of the vein. The catheter can include a
lumen to accommodate a guide wire or to allow fluid delivery.
Inventors: |
Zikorus; Arthur W. (San Jose,
CA), Parker; Mark P. (San Jose, CA), Jones; Christopher
S. (Sunnyvale, CA), Petty; Douglas M. (Pleasonton,
CA), Farley; Brian E. (Los Altos, CA), Tartaglia; Joseph
M. (Morgan Hill, CA) |
Assignee: |
VNUS Medical Technologies, Inc.
(Sunnyvale, CA)
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Family
ID: |
25454471 |
Appl.
No.: |
09/267,756 |
Filed: |
March 10, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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927251 |
Apr 11, 1997 |
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Current U.S.
Class: |
128/898; 606/37;
607/102; 607/101 |
Current CPC
Class: |
A61B
18/1492 (20130101); A61B 2018/00214 (20130101); A61B
2018/00404 (20130101); A61B 2017/00084 (20130101); A61B
2018/126 (20130101); A61B 2017/22038 (20130101); A61B
2018/1253 (20130101); A61B 2017/22051 (20130101); A61B
2018/0022 (20130101); A61B 2018/124 (20130101); A61B
2018/1475 (20130101); A61B 2090/3782 (20160201); A61B
2218/002 (20130101) |
Current International
Class: |
A61B
18/14 (20060101); A61B 17/22 (20060101); A61B
019/00 () |
Field of
Search: |
;606/32,34,40,41,42,46,48,49,50,159
;607/96,98,100-102,105,106,113,115,116 ;128/898 |
References Cited
[Referenced By]
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Other References
Electrofulgration of Varicous Veins, the Medical Letter on Drugs
and Therapeutics, Jul. 12, 1968, at 53-55. .
Watts, Endovenous Diathermy Destruction of Internal Saphenous,
British Medical Journal, Oct. 7, 1972, p. 53. .
O'Reilly, Endovenous Diathermy Sclerosis as a Unit of the
Armanentarium for the Attack on Varicose Veins, The Medical Journal
of Australia, Jun. 1, 1974, at 900. .
O'Reilly, Endovenous Diathermy Sclerosis of Varicose Veins, The
Australian New Zealand Journal of Surgery, vol. 47, No. 3, Jun.
1977, pp. 393-395. .
Brunelle, et al., A Bipolar Electrode for Vascular
Electrocoagulation with Alternating Current, Technical Notes, Oct.
1980, at 239-240. .
O'Reilly, A Technique of Diathermy Sclerosis of Varicose Veins, The
Australian New Zealand Journal of Surgery, vol. 51, No. 4, Aug.
1981, pp. 379-382. .
Cragg et al., Endovascular Diathermic Vessel Occlusion, Diagnostic
Radiology, 144:303-308, Jul. 1982. .
Ogawa, et al., Electrothrombosis As a Treatment of Cirsoid Angioma
in the Face and Scalp and Varicosis of the Leg, Plastic and
Reconstructive Surgery, Sep. 1982, vol. 3, at 310-318. .
Gradman, Venoscopic Obliteration of Variceal Tributaries Using
Monopolar Electrocautery, Journal of Dermatology Surgery Oncology,
1994, 20, p. 482-485. .
Inturri, Pathophysiology of Portal Hypertension, Journal of
Vascular Technology 19 (5-6):271-276, Sep.-Dec. 1995. .
Money, Endovascular Electroablation of Peripheral Veins, 22nd
Annual Symposium, Current Critical Problems, New Horizons and
Techniques in Vascular and Endovascular Surgery (Nov. 1995). .
Crockett, et al., Preliminary Experience with an Endovascular
Catheter for Electrocoagulation of Peripheral Veins, Journal of
Vascular Technology, Winter 1996, at 19-22..
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Primary Examiner: Leubecker; John P.
Assistant Examiner: Kearney; R.
Attorney, Agent or Firm: Fulwider Patton Lee & Utecht,
LLP
Parent Case Text
This is a divisional application of Ser. No. 08/927,251 Sep. 11,
1997.
Claims
What is claimed is:
1. A method of applying energy from a power source to a hollow
anatomical structure from within the structure, the hollow
anatomical structure having an inner wall, the method comprising
the steps of:
introducing into the hollow anatomical structure a catheter having
a working end, and a plurality of leads disposed at the working
end, each lead having a distal end, each lead being connected to
the power source;
expanding the leads outwardly from the catheter, wherein the distal
ends of the leads move away from each other and into
non-penetrating contact with the inner wall of the hollow
anatomical structure;
applying energy to the hollow anatomical structure from the distal
end of the leads until the hollow anatomical structure assumes a
significantly reduced diameter for effective ligation.
2. The method of claim 1 wherein the step of expanding the leads
comprises the step of expanding the leads such that the distal ends
of the leads are spaced such that the distal ends of the leads are
no more than 5 millimeters apart along the hollow anatomical
structure.
3. The method of claim 1 further comprising the step of extending
the leads through an orifice formed in the working end of the
catheter, wherein the distance between two mutually opposed distal
ends is greater than the diameter of the working end in the step of
expanding the distal ends when the leads are extended through the
orifice.
4. The method of claim 3 wherein separation between the leads is
maintained with an alignment device positioned inside an outer
sheath of the catheter; and further comprising the step of moving
the outer sheath in relation to the alignment device to extend the
leads out the orifice.
5. The method of claim 3 wherein separation between the leads is
maintained with an alignment device positioned inside an outer
sheath of the catheter, and the leads are attached to an inner
sheath; and further comprising the step of moving the outer sheath
in relation to the inner sheath to extend the leads through the
orifice.
6. The method of claim 3 further comprising a secondary lead
located at the working end, the secondary lead having a distal end
and having a length exceeding that of the plurality of leads; and
wherein the step of extending the plurality of leads further
includes the step of extending the secondary lead through the
distal orifice.
7. The method of claim 6 wherein the step of applying energy to the
anatomical structure comprises the steps of:
controlling the power source so that adjacent leads are of opposite
polarity while maintaining the secondary lead so that it is
electrically neutral;
switching the polarity of the leads so that they are all of the
same polarity upon collapse of the anatomical structure around the
leads; and
controlling the power source so that the secondary lead is of
opposite polarity relative to the leads upon switching the polarity
of the leads so that they are of the same polarity.
8. The method of claim 1 further comprising the step of moving the
catheter in the anatomical structure while continuing to apply
energy to the anatomical structure.
9. The method of claim 8 wherein the step of moving the catheter
comprises the step of moving the catheter in the hollow anatomical
structure along a portion of the structure while continuing to
apply energy to the anatomical structure during the movement of the
catheter as the anatomical structure collapses around the catheter
to form a lengthy effective occlusion.
10. The method of claim 1 further comprising the step of
exsanguinating the hollow anatomical structure before the step of
applying energy.
11. The method of claim 10 wherein the step of exsanguinating the
hollow anatomical structure includes the step of delivering fluid
to displace blood from the anatomical structure.
12. The method of claim 10 wherein the step of exsanguinating the
hollow anatomical structure includes the step of compressing the
hollow anatomical structure.
13. The method of claim 1 wherein the step of introducing a catcher
having a plurality of leads into the hollow anatomical structure
comprises the step of introducing a plurality of leads that are
mounted to the working end in cantilever arrangement.
14. The method of claim 1 wherein the step of expanding the leads
away from each other comprises the step of forming a bend in each
lead, the bend formed in the direction away from the other leads
such that each lead tends to move outward away from the other
leads.
15. The method of claim 1 further comprising the steps of:
moving the catheter along the hollow anatomical structure while the
leads remain in apposition with the inner wall of the hollow
anatomical structure; and
the step of applying energy occurs continually during the step of
moving the catheter.
16. The method of claim 1 further comprising the steps of:
sensing the temperature at the distal end of a lead;
controlling the application of power to the leads in response to
the temperature sensed at the distal end.
17. The method of claim 1 wherein the step of applying energy to
the anatomical structure comprises the step of controlling the
power source so that all leads are of the same potential.
18. The method of claim 1 further comprising the step of flushing
the hollow anatomical structure with fluid before the step of
applying energy.
19. The method of claim 18 wherein the step of flushing comprises
the step of delivering flushing fluid to the hollow anatomical
structure from the working end of the catheter.
20. The method of claim 19 wherein the step of delivering flushing
fluid comprises the step of conducting the flushing fluid from a
proximal end of the catheter to the working end through a lumen
adapted to receive a guide wire.
21. The method of claim 19 wherein the step of delivering flushing
fluid comprises the step of conducting the flushing fluid from a
proximal end of the catheter to the working end through a lumen
located between an outer sheath and an inner sheath.
22. The method of claim 19 wherein the step of flushing fluid
comprises the step of delivering saline to the hollow anatomical
structure.
23. The method of claim 19 wherein the step of flushing fluid
comprises the step of delivering dielectric fluid to the hollow
anatomical structure, the dielectric fluid selected to direct
energy into the tissue of the hollow anatomical structure.
24. The method of claim 19 wherein the step of flushing fluid
comprises the step of delivering heparin to the hollow anatomical
structure.
25. The method of claim 1 further comprising the step of
compressing the hollow anatomical structure before the step of
applying energy.
26. The method of claim 1 further comprising the step of
compressing the hollow anatomical structure after the step of
expanding the leads.
27. The method of claim 1 further comprising the steps of:
compressing the hollow anatomical structure with a tourniquet;
and
monitoring the hollow anatomical structure through an ultrasound
window formed in the tourniquet.
28. The method of claim 1 further comprising the step of
compressing the hollow anatomical structure so as to reduce the
diameter of the hollow anatomical structure to a desired diameter
for ligation, wherein the expanded leads are moved toward one
another by the compressed hollow anatomical structure.
29. A method of ligating a vein by applying energy to the vein from
within the vein from an energy source, the vein having an inner
wall, comprising the steps of:
introducing into the vein a catheter having a working end and a
plurality of energy delivery devices disposed at the working end,
each energy delivery device being connected to the energy
source;
bringing the energy delivery devices into non-penetrating
apposition with the inner wall of the vein;
moving the catheter along the vein while the energy delivery
devices remain in non-penetrating apposition with the inner wall of
the vein; and
applying energy to the inner wall of the vein with the energy
delivery devices during movement of the catheter such that the vein
durably assumes a significantly reduced diameter for effective
ligation.
30. The method of ligating a vein of claim 29 wherein the step of
applying energy to the inner wall of the vein comprises the step of
continually applying electrical energy to the inner wall of the
vein from the energy delivery devices during movement of the
catheter.
31. The method of ligating a vein of claim 29 further comprising
the step of expanding the energy delivery devices from the catheter
into apposition with the inner vein wall.
32. The method of ligating a vein of claim 29 wherein the step of
moving the catheter further includes the step of retracting the
catheter.
33. A method of ligating a hollow anatomical structure by applying
energy to the hollow anatomical structure from within the hollow
anatomical structure with an energy source, the hollow anatomical
structure having an inner wall, the method comprising the steps
of:
introducing into the hollow anatomical structure a catheter having
a working end and a plurality of energy delivery devices disposed
at the working end, each energy delivery device having a distal
end, each energy delivery device being connected to the energy
source;
bringing the energy delivery devices into non-penetrating
apposition with the inner wall of the hollow anatomical
structure;
compressing the hollow anatomical structure to stop blood flow and
remove blood from the hollow anatomical structure at a site where
energy is to be delivered;
delivering fluid to the hollow anatomical structure by the catheter
to prevent coagulum;
moving the catheter along the hollow anatomical structure while the
energy delivery devices remain in non-penetrating apposition with
the inner wall of the hollow anatomical structure;
sensing the temperature at an energy delivery device
controlling the application of energy to the energy delivery device
in accordance with the temperature sensed; and
continually applying energy to the inner wall of the hollow
anatomical structure with the energy delivery devices during
movement of the catheter such that the hollow anatomical structure
wall collapses around the catheter as it is being moved to create a
lengthy occlusion.
34. A method of ligating a vein by applying energy to the vein from
within the vein with an energy source, the vein having an inner
wall, the method comprising the steps of:
introducing into the vein a catheter having a working end and a
plurality of energy delivery devices disposed at the working end,
each energy delivery device having a distal end, each energy
delivery device being connected to the energy source;
bringing the energy delivery devices into non-penetrating
apposition with the inner wall of the vein;
compressing the vein to stop blood flow and remove blood from the
vein at a site where energy is to be delivered;
delivering fluid to the vein by the catheter to prevent
coagulum;
moving the catheter along the vein while the energy delivery
devices remain in non-penetrating apposition with the inner wall of
the vein;
sensing the temperature at an energy delivery device
controlling the application of energy to the energy delivery device
in accordance with the temperature sensed; and
continually applying energy to the inner wall of the vein with the
energy delivery devices during movement of the catheter such that
the vein wall collapses around the catheter as it is being moved to
create a lengthy occlusion.
35. A method of applying energy to a hollow anatomical structure
containing an ambient fluid, the method comprising the steps
of:
introducing into the hollow anatomical structure a catheter having
a working end, and a plurality of leads disposed at the working
end, each lead having a distal end;
expanding the leads outwardly from the working end of the catheter
at a treatment area within the hollow anatomical structure, wherein
the distal ends of the leads move into contact with the hollow
anatomical structure;
displacing the ambient fluid from the treatment area within the
hollow anatomical structure;
applying energy to the hollow anatomical structure from the distal
end of the leads until the hollow anatomical structure durably
assumes a significantly reduced diameter for effective
ligation.
36. The method of claim 35 wherein the step of exsanguinating the
hollow anatomical structure occurs before the step of applying
energy.
37. The method of claim 35 wherein the step of exsanguinating the
hollow anatomical structure includes the step of compressing the
hollow anatomical structure.
38. The method of claim 35 wherein the step of exsanguinating the
hollow anatomical structure includes the step of delivering fluid
to displace blood from the hollow anatomical structure.
39. The method of claim 38 wherein the step of delivering fluid
further includes the step of conducting the fluid from a proximal
end of the catheter to the working end through a lumen adapted to
receive a guide wire.
40. The method of claim 38 wherein the step of delivering fluid
further includes the step of conducting the fluid from a proximal
end of the catheter to the working end through a lumen located
between an outer sheath and an inner sheath.
41. The method of claim 38 wherein the step of delivering fluid
further includes the step of delivering dielectric fluid to the
hollow anatomical structure.
42. A method of applying energy to a hollow anatomical structure,
the method comprising the steps of:
introducing into the hollow anatomical structure a catheter having
a working end, and a plurality of arms disposed at the working end,
each arm having an energy application portion;
deploying the arms, wherein the energy application portions contact
the hollow anatomical structure;
compressing the hollow anatomical structure;
applying energy to the hollow anatomical structure from the energy
application portions until the hollow anatomical structure durably
assumes a significantly reduced diameter for effective
ligation.
43. The method of claim 42 wherein the step of compressing the
hollow anatomical structure occurs before the step of applying
energy.
44. The method of claim 42 further comprising the step of
delivering fluid to displace blood from the hollow anatomical
structure.
45. The method of claim 44 wherein the step of delivering fluid
further includes the step of delivering dielectric fluid to the
hollow anatomical structure.
46. The method of claim 42 wherein the step of compressing the
hollow anatomical structure occurs after the step of expanding the
leads.
47. The method of claim 42 wherein the step of compressing the
hollow anatomical structure further includes the step of
compressing the hollow anatomical structure with a tourniquet; and
monitoring the hollow anatomical structure through an ultrasound
window formed in the tourniquet.
48. The method of claim 42 wherein the expanded leads are moved
toward one another by the compressed hollow anatomical structure
during the step of compressing the hollow anatomical structure.
Description
BACKGROUND OF THE INVENTION
The invention relates generally to a method and apparatus for
applying energy to shrink a hollow anatomical structure such as a
vein, and more particularly, to a method and apparatus using an
electrode device having multiple leads for applying said
energy.
The human venous system of the lower limbs consists essentially of
the superficial venous system and the deep venous system with
perforating veins connecting the two systems. The superficial
system includes the long or great saphenous vein and the short
saphenous vein. The deep venous system includes the anterior and
posterior tibial veins which unite to form the popliteal vein,
which in turn becomes the femoral vein when joined by the short
saphenous vein.
The venous system contains numerous one-way valves for directing
blood flow back to the heart. Venous valves are usually bicuspid
valves, with each cusp forming a sack or reservoir for blood which,
under retrograde blood pressure, forces the free surfaces of the
cusps together to prevent retrograde flow of the blood and allows
only antegrade blood flow to the heart. When an incompetent valve
is in the flow path, the valve is unable to close because the cusps
do not form a proper seal and retrograde flow of the blood cannot
be stopped. When a venous valve fails, increased strain and
pressure occur within the lower venous sections and overlying
tissues, sometimes leading to additional valvular failure. Two
venous conditions which often result from valve failure are
varicose veins and more symptomatic chronic venous
insufficiency.
The varicose vein condition includes dilation and tortuosity of the
superficial veins of the lower limbs, resulting in unsightly
discoloration, pain, swelling, and possibly ulceration. Varicose
veins often involve incompetence of one or more venous valves,
which allow reflux of blood within the superficial system. This can
also worsen deep venous reflux and perforator reflux. Current
treatments of vein insufficiency include surgical procedures such
as vein stripping, ligation, and occasionally, vein-segment
transplant.
Ligation involves the cauterization or coagulation of vascular
lumina using electrical energy applied through an electrode device.
An electrode device is introduced into the vein lumen and
positioned so that it contacts the vein wall. Once properly
positioned, RF energy is applied to the electrode device thereby
causing the vein wall to shrink in cross-sectional diameter. A
reduction in cross-sectional diameter, as for example from 5 mm
(0.2 in) to 1 mm (0.04 in), significantly reduces the flow of blood
through the vein and results in an effective ligation. Though not
required for effective ligation, the vein wall may completely
collapse thereby resulting in a full-lumen obstruction that blocks
the flow of blood through the vein.
One apparatus for performing venous ligation includes a tubular
shaft having an electrode device attached at the distal tip.
Running through the shaft, from the distal end to the proximal end,
are electrical leads. At the proximal end of the shaft, the leads
terminate at an electrical connector, while at the distal end of
the shaft the leads are connected to the electrode device. The
electrical connector provides the interface between the leads and a
power source, typically an RF generator. The RF generator operates
under the guidance of a control device, usually a
microprocessor.
The ligation apparatus may be operated in either a monopolar and
bipolar configuration. In the monopolar configuration, the
electrode device consists of an electrode that is either positively
or negatively charged. A return path for the current passing
through the electrode is provided externally from the body, as for
example by placing the patient in physical contact with a large
low-impedance pad. The current flows from the ligation device to
the low impedance pad. In a bipolar configuration, the electrode
device consists of a pair of oppositely charged electrodes
separated by a dielectric material. Accordingly, in the bipolar
mode, the return path for current is provided by the electrode
device itself. The current flows from one electrode, through the
tissue, and returns by way of the oppositely charged electrode.
To protect against tissue damage; i.e., charring; due to
cauterization caused by overheating, a temperature sensing device
is attached to the electrode device. The temperature sensing device
may be a thermocouple that monitors the temperature of the, venous
tissue. The thermocouple interfaces with the RF generator and the
controller through the shaft and provides electrical signals to the
controller which monitors the temperature and adjusts the energy
applied to the tissue, through the electrode device,
accordingly.
The overall effectiveness of a ligation apparatus is largely
dependent on the electrode device contained within the apparatus.
Monopolar and bipolar electrode devices that comprise solid devices
having a fixed shape and size limit the effectiveness of the
ligating apparatus for several reasons. Firstly, a fixed-size
electrode device typically contacts the vein wall at only one point
on the circumference or inner diameter of the vein wall. As a
result, the application of RF energy is highly concentrated within
the contacting venous tissue, while the flow of RF current through
the remainder of the venous tissue is disproportionately weak.
Accordingly, the regions of the vein wall near the point of contact
collapse at a faster rate then other regions of the vein wall,
resulting in non-uniform shrinkage of the vein lumen. Furthermore,
the overall strength of the occlusion may be inadequate and the
lumen may eventually reopen. To avoid an inadequate occlusion RF
energy must be applied for an extended period of time. Application
of RF energy as such increases the temperature of the blood and
usually results in a significant amount of heat-induced coagulum
forming on the electrode and in the vein which is not
desirable.
Secondly, the effectiveness of a ligating apparatus having a fixed
electrode device is limited to certain sized veins. An attempt to
ligate a vein having a diameter that is substantially greater than
the electrode device can result in not only non-uniform shrinkage
of the vein wall as just described, but also insufficient shrinkage
of the vein. The greater the diameter of the vein relative to the
diameter of the electrode device, the weaker the energy applied to
the vein wall at points distant from the point of contact.
Accordingly the vein wall is likely to not completely collapse
prior to the venous tissue becoming over cauterized at the point of
electrode contact. While coagulation as such may initially occlude
the vein, such occlusion may only be temporary in that the
coagulated blood may eventually dissolve and the vein partially
open. One solution for this inadequacy is an apparatus having
interchangeable electrode devices with various diameters. Such a
solution, however, is both economically inefficient and tedious to
use.
Hence those skilled in the art have recognized a need for an
expandable electrode device and a method capable of evenly
distributing RF energy along a circumferential band of a vein wall
where the vein wall is greater in diameter than the electrode
device, and thereby provide more predictable and effective
occlusion of veins while minimizing the formation of heat-induced
coagulum. The invention fulfills these needs and others.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention provides an
apparatus and method for applying energy along a generally
circumferential band of a vein wall. The application of energy as
such results in a more uniform and predictable shrinkage of the
vein wall.
In one aspect of the invention, an apparatus for delivering energy
to ligate an anatomical structure comprises a catheter having a
sheath, a working end, and an opening formed at the working end of
the catheter; an inner member disposed within the sheath such that
the inner member and the sheath are capable of being moved relative
to one another; a plurality of leads, each lead having a distal
end, the plurality of leads being coupled with the inner member
such that the distal ends of the plurality of leads extend out of
the opening at the working end of the catheter when the position of
the sheath changes in one direction relative to the inner member,
each lead being formed to move the distal end away from a
longitudinal axis defined by the sheath when the plurality of leads
are extended out the opening; wherein the distal ends of the leads
are configured to deliver energy to the anatomical structure.
In another aspect of the invention, the apparatus includes a
secondary lead having a secondary distal end. The secondary lead is
coupled with the inner member such that the distal end of the
secondary lead is extended out of the opening at the working end of
the catheter when the position of the inner member changes in one
direction relative to the sheath.
In another aspect of the invention, the distal ends of the leads
are electrically connected to a power source such that the polarity
of each lead can be switched. Where there is a secondary lead
electrode, the plurality of leads can be connected to the power
source such that the polarity of the leads can be changed
independently of the polarity of the secondary lead.
In another aspect, the leads include primary leads which generally
surround the secondary lead at the working end of the catheter. The
distal ends of the primary leads are located between the distal end
of the secondary lead and the inner member.
In yet another aspect, the invention comprises a method of applying
energy to a hollow anatomical structure from within the structure.
The method includes the step of introducing a catheter into the
anatomical structure; the catheter having a working end and a
plurality of leads, each lead having a distal end, and each lead
being connected to a power source. The method also includes the
step of expanding the leads outwardly through the distal orifice
and expanding the leads until each electrode contacts the
anatomical structure. The method further includes the step of
applying energy to the anatomical structure from the distal end of
the leads, until the anatomical structure collapses.
In another aspect of the invention, the method also includes the
step of introducing a catheter into the anatomical structure where
the catheter has a secondary lead that has a distal portion that is
greater in length than the primary-lead distal portions and is
generally surrounded by the primary leads. The secondary lead also
has an electrode at the distal end. The method also includes the
steps of extending the primary and secondary leads through the
orifice until each primary-lead electrode contacts the anatomical
structure, and controlling the power source so that adjacent
primary leads are of opposite polarity while maintaining the
secondary-lead so that it is electrically neutral. Upon collapse of
the anatomical structure around the primary leads, the polarity of
the primary leads is switched so that they are all of the same
polarity. Upon switching the polarity of the primary leads so that
they are of the same polarity, controlling the power source so that
the secondary lead is of opposite polarity relative to the primary
leads. The method, in a further aspect, comprises the step of
moving the catheter in the anatomical structure while continuing to
apply energy to the anatomical structure to lengthen the area of
ligation.
In another aspect of the invention, external compression is used to
initially force the wall of the vein to collapse toward the
catheter. The application of energy molds the vein to durably
assume the collapsed state initially achieved mechanically by the
external compression. A tourniquet can be used to externally
compress or flatten the anatomical structure and initially reduce
the diameter of the hollow anatomical structure. The pressure
applied by the tourniquet can exsanguinate blood from the venous
treatment site, and pre-shape the vein in preparation to be molded
to a ligated state. An ultrasound window formed in the tourniquet
can be used to facilitate ultrasound imaging of the anatomical
structure being treated through the window.
These and other aspects and advantages of the present invention
will become apparent from the following more detailed description,
when taken in conjunction with the accompanying drawings which
illustrate, by way of example, embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of an energy application system with a partial
cutaway view of a catheter showing both the working end and the
connecting end and incorporating a preferred embodiment of the
present invention;
FIG. 2 is a cross-sectional view of the working end of a first
embodiment of a catheter in accordance with the invention depicting
the electrodes in a fully extended position;
FIG. 2a is an end view of the working end of the first embodiment
of the catheter taken along line 2a--2a of FIG. 2;
FIG. 3 is a cross-sectional view of the working end of the first
embodiment depicting the electrodes in a fully retracted
position;
FIG. 4 is a cross-sectional view of the working end of a second
catheter in accordance with principles of the invention depicting
the electrodes in a fully extended position;
FIG. 4a is an end view of the second embodiment of the invention
taken along line 4a--4a of FIG. 4;
FIG. 5 is a cross-sectional view of the working end of the second
embodiment of the catheter of FIG. 4 depicting the electrodes in a
fully retracted position;
FIG. 6 is a cross-sectional view of an anatomical structure
containing the catheter of FIG. 2 with the electrodes in apposition
with the anatomical structure;
FIG. 6a is an end view of the anatomical structure containing the
catheter taken along line 6a--6a of FIG. 6;
FIGS. 7a through 7c are cross-sectional views of the anatomical
structure containing a catheter in accordance with the first
embodiment of the invention and depicting the anatomical structure
at various stages of ligation;
FIG. 8 is a cross-sectional view of an anatomical structure
containing a catheter in accordance with the second embodiment of
the invention as depicted in FIG. 4;
FIG. 8a is an end view of the anatomical structure containing the
catheter taken along line 8a--8a of FIG. 8; and
FIGS. 9a and 9b are cross-sectional views of the anatomical
structure containing the catheter in accordance with the second
embodiment of the invention and depicting the anatomical structure
at various stages of ligation;
FIG. 10 is a cross-sectional view of the working end of a third
embodiment of a catheter in accordance with the invention depicting
the electrodes in a fully extended position;
FIG. 10a is an end view of the working end of the third embodiment
of the catheter taken along line 10a--10a of FIG. 10;
FIG. 11 is a cross-sectional view of the working end of the third
embodiment depicting the electrodes in a fully retracted
position;
FIG. 12 is a cross-sectional view of an anatomical structure
containing the catheter of FIG. 10 with the electrodes in
apposition with the anatomical structure;
FIG. 13 is a cross-sectional view of the anatomical structure
containing the catheter of FIG. 10 where the anatomical structure
is being ligated by the application of, energy from the
electrodes.
FIG. 14 is a cross-sectional view of an anatomical structure
containing the catheter of FIG. 10 with the electrodes in
apposition with the anatomical structure where external compression
is being applied to reduce the diameter of the hollow structure
before the application of energy from the electrodes to ligate the
structure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Turning now to the drawings with more particularity wherein like
reference numerals indicate like or corresponding elements among
the figures, shown in FIG. 1 is a catheter 10 for applying energy
to an anatomical structure such as a vein. The catheter 10 includes
an outer sheath 12 having a distal orifice 14 at its working end
15. The connector end 17 of the outer sheath 12 is attached to a
handle 16 that includes an electrical connector 18 for interfacing
with a power source 22, typically an RF generator, and a
microprocessor controller 23. The power source 22 and
microprocessor 23 are usually contained in one unit. The controller
23 controls the power source 22 in response to external commands
and data from a sensor, such as a thermocouple, located at an
intraluminal venous treatment site. In another embodiment, the user
can select a constant power output so that automated temperature
control is not present and the user can manually adjust the power
output in view of the temperature on a display readout. The
catheter 10 includes an expandable electrode device 24 (partially
shown) that moves in and out of the outer sheath 12 by way of the
distal orifice 14. The electrode device includes a plurality of
electrodes which can be expanded by moving the electrodes within
the shaft, or by moving the outer shaft relative to the electrodes.
Although FIG. 1 illustrates a plurality of electrodes surrounding a
single central electrode, different electrode configurations will
be described for the catheter.
Contained within the outer sheath 12 is an inner sheath 28 or inner
member. A fluid port 21 communicates with the interior of the outer
sheath 12. The catheter 10 can be periodically flushed out with
saline through the port 21. The flushing fluid can travel between
the outer sheath and the inner sheath. The port also allows for the
delivery of drug therapies. Flushing out the catheter prevents the
buildup of biological fluid, such as blood, within the catheter 10.
The treatment area of the hollow anatomical structure such as a
vein can be flushed with a fluid such as saline, or a dielectric
fluid, in order to evacuate blood from the treatment area of the
vein so as to prevent the formation of coagulum or thrombosis. The
use of a dielectric fluid can minimize unintended heating effects
away from the treatment area. The dielectric fluid prevents the
current of RF energy from flowing away from the vein wall.
In one embodiment, the catheter 10 includes a lumen which begins at
the distal tip of the outer sheath 12 and runs substantially along
the axis of the outer sheath 12 before terminating at the
guide-wire port 20 of the handle 16. A guide wire can be introduced
through the lumen of the catheter 10 for use in guiding the
catheter to the desired treatment site. Where the catheter is sized
to treat smaller veins, the outer diameter of the catheter may not
allow for a fluid flush between the outer sheath 12 and the inner
sheath 28. However, a fluid flush can be introduced through the
lumen for the guide wire in such an embodiment.
Referring now to FIGS. 2, 2a, 3, 4, 4a and 5, the outer sheath 12
includes a shell 44 and a tip portion 46. To provide an atraumatic
tip for the catheter 10 as it is manipulated through the vein, the
tip 46 is preferably tapered inward at its distal end or is
"nosecone" shaped. The tip 46, however, can have other shapes that
facilitate tracking of the catheter 10 over a guide wire and
through the bends in the venous vascular system. The
nosecone-shaped tip 46 can, for example, be fabricated from a
polymer having a soft durometer, such as 70 Shore A. The shell 44
comprises a biocompatible material having a low coefficient of
friction. In one configuration, the outer sheath 12 is sized to fit
within a venous lumen and for example may be between 5 and 9
French, which corresponds to a diameter of between 1.7 mm (0.07 in)
and 3.0 mm (1.2 in), or other sizes as appropriate.
The electrode device 24 contains a number of leads, including
insulated primary leads 30 and, in some embodiments, a secondary
lead 31. Preferably, the leads are connected to the power source 22
(FIG. 1) such that the polarity of the leads may be switched as
desired. Alternately, a microprocessor controller can be used to
switch the polarity, as well as control other characteristics of
the power for the electrode device. Thus the electrode device can
operate in either a bipolar or a monopolar configuration. When
adjacent primary leads 30 have opposite polarity the electrode
device 24 operates as a bipolar electrode device. When the primary
leads 30 are commonly charged the electrode device 24 can operate
as a monopolar electrode device. When the primary leads 30 are
commonly charged, and a secondary lead 31 has an opposite polarity,
the electrode device 24 operates as a bipolar electrode device. The
embodiment of the invention shown in FIGS. 2 and 3 depict an
electrode device 24 having four primary leads 30 and a secondary
lead 31, while the embodiment of the invention shown in FIGS. 4 and
5 depict an electrode device 24 having only four primary leads. The
invention is not limited to four primary leads 30; more or fewer
leads may be used in either embodiment. The number of leads can be
dependent on the size or diameter of the hollow anatomical
structure to be treated. The apposed electrodes should be kept
within a certain distance of one another. Larger vessels may
require more primary leads to ensure proper current density and
proper heat distribution.
The insulation on each of the leads 30, 31 may be removed at the
distal end 32, 33 to expose the conductive wire. In the first
configuration as shown in FIGS. 2, 2a, and 3, the electrode 34 has
a hemispherical shape. In a second configuration, the electrode can
have either a generally spherical shape or a spoon shape. As shown
in FIGS. 4, 4a and 5, the electrodes have a spoon shape which can
be combined to form a sphere or other shape so as to minimize its
profile when the vein collapses. The electrodes 34 are either
integrally formed at the distal end 32, soldered, or otherwise
formed to the distal end of each primary lead 30. It is to be
understood that when the distal end 32 is referred to as acting as
an electrode, this is not limited to where the electrode 34 is
integrally formed at the distal end 32. For example, the distal end
can apply energy to the surrounding tissue where there is an
electrode integrally formed at the distal end, or where an
electrode is separately soldered to the distalend, or where there
is another energy delivery device located at the distal end. The
electrode 34 typically has a diameter greater than the diameter of
the primary lead 30. For example, the primary lead 30 may have a
diameter ranging from 0.18 mm (0.007 in.) to 0.28 mm (0.011 in.),
while the electrode 34 has a diameter of 0.36 mm (0.014 in.) to
0.51 mm (0.020 in.). The primary leads 30 and the electrodes 34 are
preferably made from a biologically-compatible material such as
stainless steel. The insulation surrounding the primary leads 30
generally has a thickness of between 0.03 mm (0.001 in.) and 0.06
mm (0.0025 in.), resulting in a combined lead-insulation diameter
of between 0.23 mm (0.009 in.) and 0.41 mm (0.016 in.). In an
alternate configuration, as shown in FIGS. 2 and 3, each primary
lead 30 is strip-shaped with a width from 0.76 mm (0.03 in.) to 1.0
mm (0.04 in) and a thickness of approximately 0.13 mm (0.005 in.),
while the secondary lead 31 is typically tubular-shaped. It should
be noted that these dimensions are provided for illustrative
purposes, and not by way of limitation. A hemispherically shaped
electrode 34 is formed at the distal end, as for example, by
sanding down a sixteenth-inch (1.6 mm) diameter sphere which is
soldered to the distal end 32 of the primary lead 30. The
electrodes can also be constructed by stamping the desired shape or
configuration from the conductive lead. The electrode is integral
with the lead, and the remainder of the lead is insulated. The
distal end 33 of the secondary lead 31 preferably includes a
generally spherically-shaped electrode 35.
An alignment device 36 arranges the leads 30, 31 such that they are
mounted to the catheter at only their proximal ends and so that
separation is maintained between the leads within, and distal to
the alignment device. The leads can form cantilevers when mounted
on the alignment device. A preferred configuration of the alignment
device 36 includes a plurality of off-center, axially-aligned
lumina 38 which are substantially symmetrically positioned relative
to the axis of the alignment device 36. The alignment device 36 is
formed, for example, by extruding the plurality of axially-aligned
lumina 38 through a solid cylinder composed of a dielectric
material, such as polyamide. Each lead 30 passes through an
individual off-center lumen 38 and exits out the rear of the
alignment device 36. The alignment device 36 may further include a
central lumen 48 that may be aligned with the axis. In some
embodiments the central lumen 48 is used for accepting a guide wire
or for the delivery or perfusion of medicant and cooling solution
to the treatment area during application of RF energy. In other
embodiments, the central lumen 48 may be used for the secondary
lead 31. The alignment device 36 may also further include an
auxiliary lumen 47 for additional leads, such as the leads of, a
thermocouple used as a temperature sensor. The alignment device 36
comprises a dielectric material to prevent or minimize any coupling
effect the leads 30, 31 may have with each other and, if present,
the guide wire. The length of the alignment device is, for example,
12.5 mm (0.5 in.) to 19.0 mm (0.75 in.) in one embodiment. However,
these dimensions are provided for purposes of illustration and not
by way of limitation.
In the embodiment of the invention shown in FIGS. 2, 2a and 3, the
inner sheath 28 is attached to the alignment device 36 and extends
beyond the rear 37 of the alignment device. Preferably, the inner
sheath 28 completely surrounds the exterior wall of the alignment
device 36 and is mounted to it by adhesive or press fit or in other
manner such that it remains in a fixed position relative to the
inner sheath. The inner sheath and alignment device can act as an
inner member relative to the outer sheath. The inner sheath 28
comprises a biocompatible material with a low coefficient of
friction. The inner sheath 28 provides a pathway for the
interconnection between the leads 30, 31 and the electrical
connector 18 (FIG. 1). This interconnection may occur in any of
several ways. The leads 30, 31 themselves may be continuous and run
the entire length of the inner sheath 28. In the alternative (not
shown), the positively charged leads 30, 31 may couple with a
common positively charged conductor housed in the inner sheath 28.
Likewise, the negatively charged leads 30, 31 may couple with a
common negative conductor. Preferably, the leads 30, 31 are
connected to a conductor that allows for the polarity of the leads
to be switched. The conductor may comprise, for example, a 36 gauge
copper lead with a polyurethane coating. The coupling may occur at
any point within the inner sheath 28. To reduce the amount of wire
contained in the catheter, it is advantageous to couple the leads
30, 31 at the point where the leads exit the rear 37 of the
alignment device 36. To add further stability to the electrode
device 24, it is preferred that bonding material 40 surround the
leads 30, 31 at the front end of the alignment device 36. In this
embodiment, the leads 30, 31 exit through the distal orifice 14 as
the outer sheath 12 is retracted backwards over the alignment
device 36. The inwardly tapered tip 46 impedes the retracting
movement of the outer sheath 12 to prevent the exposure of the
alignment device 36.
FIG. 3 shows the leads 30 and 31 in the retracted position where
all leads are within the nosecone-shaped tip portion 46 and the
outer shell 44. The alignment device 36 has been moved relative to
the outer shell 44. The soft nosecone provides an atraumatic tip
for when the catheter is maneuvered through the tortuous venous
system. The electrode at the distal end of the secondary lead 31
can be sized to approximately the same size as the opening formed
in the nosecone 46. The nosecone forms a closed atraumatic tip
together with the electrode of the secondary lead when the
alignment device is retracted into the outer sheath of the
catheter. This can present an atraumatic tip even where the
nosecone is not constructed from a material having a soft
durometer.
Referring now to FIGS. 4 and 5, in another embodiment, the
alignment device 36 is attached to the outer sheath 12 and thereby
remains immobile in relation to it. The inner sheath 28 is movably
positioned at the rear of the alignment device 36 and again
provides a pathway for the interconnection between the primary
leads 30 and the electrical connector 18 (FIG. 1). In some
embodiments the inner sheath 28 contains a guide-wire tube 49 that
runs the entire length of the inner sheath. The guide-wire tube 49
is aligned to communicate with the central lumen 48 of the
alignment device 36 at one end and with the guide-wire port 20
(FIG. 1) at the other end. The primary leads 30 may be continuous
and run the entire length of the inner sheath 28 or they may be
coupled to common leads as previously described. The primary leads
30 are secured to the front end 27 of the inner sheath 28, as for
example with a potting material 50, so that the movement of the
inner sheath 28 results in a corresponding movement of the primary
leads 30 through the lumina 38 of the alignment device 36. In this
embodiment, the primary leads 30 are not secured to the alignment
device 36 and in essence are free-floating leads in the axial
direction. The primary leads 30 travel through the alignment device
36 and exit through the distal orifice 14 as the front end of the
inner sheath 28 is moved toward the rear 37 of the alignment device
36.
In the above embodiments, the primary leads 30 are formed, e.g.,
arced or bent, to move away from each other and thereby avoid
contact. The "distal portion" of the primary leads 30 is the
portion of the lead which extends from the front end of the
alignment device 36 when the leads are fully extended through the
distal orifice 14. It is preferred that the distal portions 42 are
formed to move radially outward from each other relative to the
axis of the alignment device 36 and form a symmetrical arrangement.
This is shown in both the embodiments of FIG. 2a and FIG. 4a. The
degree of arc or bend in the primary leads 30 may be any that is
sufficient to radially expand the leads as they exit the outer
sheath 12 through the distal orifice 14. It is essential that the
degree of the arc or bend be sufficient to provide enough force so
that the primary leads 30 expand through blood and the electrodes
34 come in apposition with the vein wall. The electrodes are
preferably partially embedded in the vein wall to assure full
contact. The rounded portion of the electrode is embedded into the
vein wall to achieve full surface apposition so that the entire
uninsulated surface area of the electrode is in contact with venous
tissue for effective current distribution. The surface area of the
electrodes in contact with the venous tissue preferably is
sufficient to avoid a high current density which may lead to spot
heating of the venous tissue. The heating effect is preferably
distributed along a circumferential band of the vein. The apposed
electrodes should be spaced no more than 4 or 5 millimeters from
one another along the circumference of the vein. Thus, the
electrode arrangement is related to the size or diameter of the
vein being treated. Other properties of the primary leads 30, such
as lead shape and insulation thickness, affect the push force of
the lead and the degree of arc or bend must be adjusted to
compensate for these factors. For example, in one configuration of
the electrode device 24, a wire having a diameter of between 0.18
mm (0.007 in) and 0.28 mm (0.011 in) with a total insulation
thickness of between 0.05 mm (0.002 in) to 0.13 mm (0.005 in) is
arced or bent at an acute angle to provide sufficient apposition
with the anatomical structure. It is to be understood that these
dimensions are provided for illustrative purposes, and not by way
of limitation.
Other techniques for expanding the leads outwardly once they have
been extended from the working end of the catheter may be possible.
For example, the leads may be straight but are mounted in the
alignment device at an angle such that they are normally directed
outward.
For increased appositional force, it is preferred that the primary
leads 30 be strip-shaped, that is rectangular in cross section,
with dimensions, for example, of a width from 0.76 mm (0.030 in.)
to 1.0 mm (0.039 in) and a thickness of approximately 0.13 mm
(0.005 in.). The rectangular cross section provides increased
resistance to bending in the width dimension but allows bending
more freely in the thickness dimension. This strip-shaped
configuration of the primary leads 30 is shown in FIGS. 2, 2a, and
3 and provides for increased stability in the lateral direction
while allowing the necessary bending in the radial direction. In
FIGS. 2, 2a, and 3, each primary lead comprises a rectangular cross
section mounted in relation to the catheter such that the thinner
dimension of the rectangular cross section is aligned with the
direction of expansion of the lead. The leads are less likely to
bend sideways when expanded outward, and a uniform spacing between
leads is more assured. Uniform spacing promotes uniform heating
around the venous tissue which is in apposition with the electrodes
at the distal ends of the leads.
The length of the distal portion of the leads 30 also affects the
configuration of the electrode device 24. The maximum distance
between two mutually opposed electrodes 34; i.e., the effective
diameter of the electrode device 24, is affected by the bend degree
and length of the distal portion 42. The longer the length of the
distal portion 42 the greater the diameter of the electrode device
24. Accordingly, by changing the distal portion 42 length and arc
or bend degree, the catheter 10 can be configured for use in
differently sized anatomical structures.
Different numbers of leads 30, 31 can be employed with the
catheter. The number of leads 30, 31 is limited by the diameter of
the alignment device 36 and the number of lumina 36, 38, 47 that
can be extruded through the alignment device. In a bipolar
configuration, an even number of primary leads 30 are preferably
available to form a number of oppositely charged electrode pairs.
The electrodes in appostion with the anatomical structure should be
maintained within a certain distance of each other. In a monopolar
configuration, any number of commonly charged leads 30 can be
present. In the monopolar mode, distribution of RF energy through
the anatomical tissue is obtained by creating a return path for
current through the tissue by providing a return device at a point
external from the tissue, such as a large metal pad.
Now referring again to FIG. 1, an actuator 25 controls the
extension of the electrode device 24 through the distal orifice 14.
The actuator 25 may take the form of a switch, lever, threaded
control knob, or other suitable mechanism, and is preferably one
that can provide fine control over the movement of the outer sheath
12 or the inner sheath 28, as the case may be. In one embodiment of
the invention, the actuator 25 (FIG. 1) interfaces with the outer
sheath 12 (FIGS. 2, 2a and 3) to move it back and forth relative to
the inner sheath 28. In another embodiment the actuator 25 (FIG. 1)
interfaces with the inner sheath 28 (FIGS. 4, 4a and 5) to move it
back and forth relative to the outer sheath 12. The relative
position between the outer sheath and inner sheath is thus
controlled, but other control approaches may be used.
Referring again to FIGS. 2, 2a, 3, 4, 4a and 5, the catheter 10
includes a temperature sensor 26, such as a thermocouple. The
temperature sensor 26 is mounted in place on an electrode 34 so
that the sensor 26 is nearly or is substantially flush with the
exposed surface of the electrode 34. The sensor 26 is shown in the
drawings as protruding from the electrodes for clarity of
illustration only. The sensor 26 senses the temperature of the
portion of the anatomical tissue that is in apposition with the
exposed electrode surface. Monitoring the temperature of the
anatomical tissue provides a good indication of when shrinkage of
the tissue is ready to begin. A temperature sensor 26 placed on the
electrode facing the anatomical tissue provides an indication of
when shrinkage occurs (70.degree. C. or higher) and when
significant amounts of heat-induced coagulum may begin to form on
the electrodes (at 85.degree. C. or higher). Therefore maintaining
the temperature above 70 degrees Centigrade produces a therapeutic
shrinkage of the anatomical structure. Application of the RF energy
from the electrodes 34 is halted or reduced when the monitored
temperature reaches or exceeds the specific temperature that was
selected by the operator, typically the temperature at which
anatomical tissue begins to cauterize. The temperature sensor 26
interfaces with the controller 23 (FIG. 1) through a pair of sensor
leads 45 which preferably run through the auxiliary lumen 47 and
then through the inner sheath 28. The signals from the temperature
sensor 26 are provided to the controller 23 which controls the
magnitude of RF energy supplied to the electrodes 34 in accordance
with the selected temperature criteria and the monitored
temperature. Other techniques such as impedance monitoring, and
ultrasonic pulse echoing can be utilized in an automated system
which shuts down or regulates the application of RF energy from the
electrodes to the venous section when sufficient shrinkage of the
vein is detected and to avoid overheating the vein.
Referring now to FIGS. 6, 6a and 7a through 7c, in the operation of
one embodiment of the catheter 10, the catheter is inserted into a
hollow anatomical structure, such as a vein 52. The catheter is
similar to the embodiment discussed in connection with FIGS. 2 and
3. The catheter 10 further includes an external sheath 60 through
which a fluid can be delivered to the treatment site. In this
embodiment, the fluid port (not shown) communicates with the
interior of the external sheath 60, and fluid is delivered from
between the external sheath 60 and the outer sheath 12. The
external sheath 60 surrounds the outer sheath 12 to form a coaxial
channel through which fluid may be flushed.
Fluoroscopy, ultrasound, an angioscope imaging technique, or other
technique may be used to direct the specific placement of the
catheter and confirm the position in the vein. The actuator (not
shown) is then operated to shift the outer sheath relative to the
inner sheath by either retracting the outer sheath 12 backward or
advancing the inner sheath 28 forward to expose the leads 30, 31
through the distal orifice 14. As the leads 30, 31 exit the distal
orifice 14, the primary leads 30 expand radially outward relative
to the axis of the alignment device 36, while the secondary lead 31
remains substantially linear. The primary leads 30 continue to move
outward until apposition with the vein wall 54 occurs and the
outward movement of the primary leads 30 is impeded. The primary
leads 30 contact the vein along a generally circumferential band of
the vein wall 54. This outward movement of the primary leads 30
occurs in a substantially symmetrical fashion. As a result, the
primary-lead electrodes 34 are substantially evenly spaced along
the circumferential band of the vein wall 54. The central-lead
electrode 35 is suspended within the vein 52 without contacting the
vein wall 54.
When the electrodes 34 are positioned at the treatment site of the
vein, the power supply 22 is activated to provide suitable RF
energy, preferably at a selected frequency from a range of 250 kHz
to 350 MHZ. One suitable frequency is 510 kHz. One criterion used
in selecting the frequency of the energy to be applied is the
control desired over the spread, including the depth, of the
thermal effect in the venous tissue. Another criterion is
compatibility with filter circuits for eliminating RF noise from
thermocouple signals.
In bipolar operation, the primary leads 30 are initially charged
such that adjacent leads are oppositely charged while the secondary
lead is electrically neutral. These multiple pairs of oppositely
charged leads 30 form active electrode pairs to produce an RF field
between them. Thus, discrete RF fields are set up along the
circumferential band of the vein wall 54. These discrete fields
form a symmetrical RF field pattern along the entire
circumferential band of the vein wall 54, as adjacent electrodes 34
of opposite polarity produce RF fields between each other. A
uniform temperature distribution can be achieved along the vein
wall being treated.
The RF energy is converted within the adjacent venous tissue into
heat, and this thermal effect causes the venous tissue to shrink,
reducing the diameter of the vein. A uniform temperature
distribution along the vein wall being treated avoids the formation
of hot spots in the treatment area while promoting controlled
uniform reduction in vein diameter. The thermal effect produces
structural transfiguration of the collagen fibrils in the vein. The
collagen fibrils shorten and thicken in cross-section in response
to the heat from the thermal effect. As shown in FIG. 7a, the
energy causes the vein wall 54 to collapse around the primary-lead
electrodes 34. The wall 54 continues to collapse until further
collapse is impeded by the electrodes 34. The electrodes are
pressed farther and farther together by the shrinking vein wall 54
until they touch and at that point, further collapse or ligation of
the wall 54 is impeded. Upon collapse of the vein wall 54 around
the primary-lead electrodes 34, the polarity of the primary-lead
electrodes is switched so that all primary-lead electrodes are
commonly charged. The switching of polarity for the leads need not
be instantaneous. The application of RF energy can be ceased, the
polarity switched, and then RF energy is applied again at the
switched polarity. The secondary-lead electrode 35 is then charged
so that its polarity is opposite that of the primary-lead
electrodes 34. The RF field is set up between the primary-lead
electrodes 34 and the secondary-lead electrode 35.
The catheter 10 is then pulled back while energy is applied to the
electrode device. As shown in FIG. 7b, while the catheter 10 is
being pulled back, the primary-lead electrodes 34 remain in
apposition with the vein wall 54 while the secondary-lead electrode
35 comes in contact with the portion of the vein wall previously
collapsed by the primary-lead electrodes 34. Accordingly, RF energy
passes through the vein wall 54 between the primary-lead electrodes
34 and the secondary-lead electrode 35 and the vein wall continues
to collapse around the secondary-lead electrode 35 as the catheter
is being retracted. As shown in FIG. 7c, ligation in accordance
with this method results in an occlusion along a length of the vein
52. A lengthy occlusion, as opposed to an acute occlusion, is
stronger and less susceptible to recanalization.
A similar result is achieved when the catheter 10 having both
primary and secondary leads is operated in a monopolar manner. In a
monopolar operation, the secondary-lead electrode 35 remains
neutral, while the primary leads 30 are commonly charged and act in
conjunction with an independent electrical device, such as a large
low-impedance return pad (not shown) placed in external contact
with the body, to form a series of discrete RF fields. These RF
fields are substantially evenly spaced around the circumference of
the vein and travel along the axial length of the vein wall causing
the vein wall to collapse around the primary-lead electrodes. Upon
collapse of the vein wall, the secondary-lead electrode is charged
to have the same polarity as that of the primary-lead electrodes.
The electrode device is retracted and the vein wall collapses as
described in the bipolar operation.
In either bipolar or monopolar operation the application of RF
energy is substantially symmetrically distributed through the vein
wall, regardless of the diameter of the vein 52. This symmetrical
distribution of RF energy increases the predictability and
uniformity of the shrinkage and the strength of the occlusion.
Furthermore, the uniform distribution of energy allows for the
application of RF energy for a short duration and thereby reduces
or avoids the formation of heat-induced coagulum on the electrodes
34. The leads, including the non-convex outer portion of the
electrode, are insulated to further prevent heating of the
surrounding blood.
Fluid can be delivered before and during RF heating of the vein
being treated through a coaxial channel formed between the external
sheath 60 and the outer sheath 12. It is to be understood that
another lumen can be formed in the catheter to deliver fluid to the
treatment site. The delivered fluid displaces or exsanguinates
blood from the vein so as to avoid heating and coagulation of
blood. Fluid can continue to be delivered during RF treatment to
prevent blood from circulating back to the treatment site. The
delivery of a dielectric fluid increases the surrounding impedance
so that RF energy is directed into the tissue of the vein wall.
Referring now to FIGS. 8, 8a, 9a and 9b, in the operation of an
alternate embodiment of the catheter 10 that may be used with a
guide wire 53. As in the previous embodiment, the catheter 10 is
inserted into a hollow anatomical structure, such as a vein 52. The
guide wire 53 is advanced past the point where energy application
is desired. The catheter 10 is then inserted over the guide wire 53
by way of the central lumen 48 and the guide wire tube 49 (FIG. 4)
and is advanced over the guide wire through the vein to the desired
point. The guide wire 53 is typically pulled back or removed before
RF energy is applied to the electrode device 24.
The actuator 25 (FIG. 1) is then manipulated to either retract the
outer sheath 12 backward, or advance the inner sheath 28 forward to
expose the leads 30 through the distal orifice 14. The leads 30
exit the distal orifice 14 and expand radially outward relative to
the axis of the alignment device 36. The leads 30 continue to move
outward until apposition with the vein wall 54 occurs. The leads 30
contact the vein along a generally circumferential band of the vein
wall 54. This outward movement of the leads occurs in a
substantially symmetrical fashion. As a result, the electrodes 34
are substantially evenly spaced along the circumferential band of
the vein wall 54. Alternately, the electrodes can be spaced apart
in a staggered fashion such that the electrodes do not lie along
the same plane. For example, adjacent electrodes can extend
different lengths from the catheter so that a smaller
cross-sectional profile is achieved when the electrodes are
collapsed toward one another.
When the electrodes 34 are positioned at the treatment site of the
vein, the power supply 22 is activated to provide suitable RF
energy to the electrodes 34 so that the catheter 10 operates in
either a bipolar or monopolar manner as previously described. As
shown in FIGS. 9a and 9b, the energy causes the vein wall 54 to
collapse around the electrodes 34 causing the leads to
substantially straighten and the electrodes to cluster around each
other. The wall 54 continues to collapse until further collapse is
impeded by the electrodes 34 (FIG. 9b). At this point the
application of energy may cease. The electrodes can be configured
to form a shape with a reduced profile when collapsed together. The
electrodes can also be configured and insulated to continue
applying RF energy after forming a reduced profile shape by the
collapse of the vein wall. The catheter 10 can be pulled back to
ligate the adjacent venous segment. If a temperature sensor 26 is
included, the application of energy may cease prior to complete
collapse if the temperature of the venous tissue rises above an
acceptable level as defined by the controller 23.
Where the catheter includes a fluid delivery lumen (not shown),
fluid can be delivered before and during RF heating of the vein
being treated. The fluid can displace blood from the treatment area
in the vein to avoid the coagulation of blood. The fluid can be a
dielectric medium. The fluid can include an anticoagulant such as
heparin which can chemically discourage the coagulation of blood at
the treatment site.
After completing the procedure for a selected venous section, the
actuator mechanism causes the primary leads to return to the
interior of the outer sheath 12. Either the outer sheath or the
inner sheath is moved to change the position of the two elements
relative to one another. Once the leads 30 are within the outer
sheath 12, the catheter 10 may be moved to another venous section
where the ligation process is repeated. Upon treatment of all
venous sites, the catheter 10 is removed from the vasculature. The
access point of the vein is then sutured closed, or local pressure
is applied until bleeding is controlled.
Another embodiment of the catheter is illustrated in FIG. 10. The
inner member or sheath 28 is contained within the outer sheath 12.
The inner sheath is preferably constructed from a flexible polymer
such as polyimide, polyethylene, or nylon, and can travel the
entire length of the catheter. The majority of the catheter should
be flexible so as to navigate the tortuous paths of the venous
system. A hypotube having a flared distal end 33 and a circular
cross-sectional shape is attached over the distal end of the inner
sheath 28. The hypotube is preferably no more than about two to
three centimeters in length. The hypotube acts as part of the
conductive secondary lead 31. An uninsulated conductive electrode
sphere 35 is slipped over the hypotube. The flared distal end of
the hypotube prevents the electrode sphere from moving beyond the
distal end of the hypotube. The sphere is permanently affixed to
the hypotube, such as by soldering the sphere both front and back
on the hypotube. The majority or the entire surface of the
spherical electrode 35 remains uninsulated. The remainder of the
hypotube is preferably insulated so that the sphere-shaped distal
end can act as the electrode. For example, the hypotube can be
covered with an insulating material such as a coating of parylene.
The interior lumen of the hypotube is lined by the inner sheath 28
which is attached to the flaired distal end of the hypotube by
adhesive such as epoxy.
Surrounding the secondary lead 31 and sphere-shaped electrode 35
are a plurality of primary leads 30 which preferably have a flat
rectangular strip shape and can act as arms. As illustrated in FIG.
11, the plurality of primary leads are preferably connected to
common conductive rings 62. This configuration maintains the
position of the plurality of primary leads, while reducing the
number of internal electrical connections. The rings 62 are
attached to the inner sheath 28. The position of the rings and the
primary leads relative to the outer sheath follows that of the
inner sheath. As earlier described, the hypotube of the secondary
lead 31 is also attached to the inner sheath 28. Two separate
conductive rings can be used so that the polarity of different
primary leads can be controlled separately. For example, adjacent
primary leads can be connected to one of the two separate
conductive rings so that the adjacent leads can be switched to have
either opposite polarities or the same polarity. The rings are
preferable spaced closely together, but remain electrically
isolated from one another along the inner sheath. Both the rings
and the hypotube are coupled with the inner sheath, and the primary
leads 30 that are connected to the rings move together with and
secondary lead while remaining electrically isolated from one
another. Epoxy or another suitable adhesive can be used to attach
the rings to the inner sheath. The primary leads from the
respective rings each alternate with each other along the
circumference of the inner sheath. The insulation along the
underside of the leads prevents an electrical short between the
rings.
The ring and primary leads are attached together to act as
cantilevers where the ring forms the base and the rectangular
primary leads operate as the cantilever arms. The leads 30 are
connected to the ring and are formed to have an arc or bend such
that the leads act as arms which tend to spring outwardly away from
the catheter and toward the surrounding venous tissue. Insulation
along the underside of the leads and the rings prevents unintended
electrical coupling between the leads and the opposing rings.
Alternately, the leads are formed straight and connected to the
ring at an angle, such that the leads tend to expand or spring
radially outward from the ring. The angle at which the leads are
attached to the ring should be sufficient to force the primary
distal ends and electrodes 34 through blood and into apposition
with the vein wall. Other properties of the primary leads 30, such
as lead shape and insulation thickness, affect the push force of
the lead and the degree of arc or bend must be adjusted to
compensate for these factors. The rectangular cross section of the
leads 30 can provide increased stability in the lateral direction
while allowing the necessary bending in the radial direction. The
leads 30 are less likely to bend sideways when expanded outward,
and a uniform spacing between leads is more assured. Uniform
spacing between the leads 30 and the distal ends promotes uniform
heating around the vein by the electrodes 34.
The distal ends of the primary leads 30 are uninsulated to act as
electrodes 34 having a spoon or hemispherical shape. The leads can
be stamped to produce an integral shaped electrode at the distal
end of the lead. The uninsulated outer portion of the distal end
electrode 34 which is to come into apposition with the wall of the
anatomical structure is preferably rounded and convex. The
flattened or non-convex inner portion of the distal end is
insulated to minimize any unintended thermal effect, such as on the
surrounding blood in a vein. The distal end electrodes 34 are
configured such that when the distal ends are forced toward the
inner sheath 12, as shown in FIG. 10a, the distal ends combine to
form a substantially spherical shape with a profile smaller than
the profile for the spherical electrode 35 at the secondary distal
end.
The outer sheath 12 can slide over and surround the primary and
secondary leads 30, 31. The outer sheath 12 includes an orifice
which is dimensioned to have approximately the same size as the
spherical electrode 35 at the secondary distal end which functions
as an electrode. A close or snug fit between the electrode 35 at
the secondary distal end and the orifice of the outer sheath 12 is
achieved. This configuration provides an atruamatic tip for the
catheter. The electrode 35 secondary distal end is preferably
slightly larger than the orifice. The inner diameter of the outer
sheath 12 is approximately the same as the reduced profile of the
combined primary distal end electrodes 34. The diameter of the
reduced profile of the combined primary distal end electrodes 34 is
preferably less than the inner diameter of the outer sheath.
A fluid port (not shown) can communicate with the interior of the
outer sheath 12 so that fluid can be flushed between the outer
sheath 12 and the inner sheath 28. Alternately, a fluid port can
communicate with a central lumen 48 in the hypotube which can also
accept a guidewire. As previously stated, the catheter 10 can be
periodically flushed with saline which can prevent the buildup of
biological fluid, such as blood, within the catheter 10. A guide
wire can be introduced through the lumen 48 for use in guiding the
catheter to the desired treatment site. As previously described, a
fluid can be flushed or delivered though the lumen as well. If a
central lumen is not desired, the lumen of the hypotube can be
filled with solder.
Preferably, the primary leads 30 and the connecting rings are
connected to a power source 22 such that the polarity of the leads
may be switched as desired. This allows for the electrode device 24
to operate in either a bipolar or a monopolar configuration. When
adjacent primary leads 30 have opposite polarity, a bipolar
electrode operation is available. When the primary leads 30 are
commonly charged a monopolar electrode operation is available in
combination with a large return electrode pad placed in contact
with the patient. When the primary leads 30 are commonly charged,
and a secondary lead 31 has an opposite polarity, a bipolar
electrode operation is available. More or fewer leads may be used.
The number of leads can be dependent on the size or diameter of the
hollow anatomical structure to be treated.
Although not shown, it is to be understood that the catheter 10 can
include a temperature sensor, such as a thermocouple, mounted in
place on the distal end or electrode 34 so that the sensor is
substantially flush with the exposed surface of the electrode 34.
The sensor senses the temperature of the portion of the anatomical
tissue that is in apposition with the exposed electrode surface.
Application of the RF energy from the electrodes 34 is halted or
reduced when the monitored temperature reaches or exceeds the
specific temperature that was selected by the operator, such as the
temperature at which anatomical tissue begins to cauterize. Other
techniques such as impedance monitoring, and ultrasonic pulse
echoing can be utilized in an automated system which shuts down or
regulates the application of RF energy from the electrodes to the
venous section when sufficient shrinkage of the vein is detected
and to avoid overheating the vein.
Referring now to FIGS. 12 through 14, in the operation of one
embodiment of the catheter 10, the catheter is inserted into a
hollow anatomical structure, such as a vein. Fluoroscopy,
ultrasound, an angioscope imaging technique, or another technique
may be used to direct and confirm the specific placement of the
catheter in the vein. The actuator is then operated to retract the
outer sheath 12 to expose the leads 30, 31. As the outer sheath no
longer restrains the leads, the primary leads 30 move outward
relative to the axis defined by the outer sheath, while the
secondary lead 31 remains substantially linear along the axis
defamed by the outer sheath. The primary leads 30 continue to move
outward until the distal end electrode 34 of the primary leads are
placed in apposition with the vein wall 54 occurs and the outward
movement of the primary leads 30 is impeded. The primary leads 30
contact the vein along a generally circumferential area of the vein
wall 54. This outward movement of the primary leads 30 occurs in a
substantially symmetrical fashion so that the primary distal end
electrodes 34 are substantially evenly spaced. The central-lead
electrode 35 is suspended within the vein without contacting the
vein wall 54.
When the electrodes 34 are positioned at the treatment site of the
vein, the power supply 22 is activated to provide suitable RF
energy. In a bipolar operation, the primary leads 30 are initially
charged such that adjacent leads are oppositely charged while the
secondary lead is electrically neutral. These multiple pairs of
oppositely charged leads 30 form active electrode pairs to produce
an RF field between them, and form a symmetrical RF field pattern
along a circumferential band of the vein wall to achieve a uniform
temperature distribution along the vein wall being treated.
The RF energy produces a thermal effect which causes the venous
tissue to shrink, reducing the diameter of the vein. As shown in
FIG. 13, the energy causes the vein wall 54 to collapse until
further collapse is impeded by the electrodes 34. The electrodes
are pressed closer together by the shrinking vein wall. The
electrodes 34 are pressed together to assume a reduced profile
shape which is sufficiently small so that the vein is effectively
ligated. Upon collapse of the vein wall 54 around the primarylead
electrodes 34, the polarity of the primary-lead electrodes is
switched so that all of the primary-lead electrodes are commonly
charged. The secondary-lead electrode 35 is then charged so that
its polarity is opposite that of the primary-lead electrodes 34.
Where the primary electrodes 34 and the secondary electrode 35 are
spaced sufficiently close together, when the vein wall collapses
around the primary lead electrodes, the electrode at the distal end
of the secondary lead can also come into contact with the a portion
of the vein wall so that an RF field is created between the primary
electrodes 34 and the secondary electrode 35.
The catheter 10 is pulled back to ensure apposition between the
electrodes at the distal ends of the leads and the vein wall. When
the catheter 10 is being pulled back, the primary-lead electrodes
34 remain in apposition with the vein wall 54 while the
secondary-lead electrode 35 comes in contact with the portion of
the vein wall previously collapsed by the primary-lead electrodes
34. RF energy passes through the venous tissue between the
primary-lead electrodes 34 and the secondary-lead electrode 35.
Ligation as the catheter is being retracted produces a lengthy
occlusion which is stronger and less susceptible to recanalization
than an acute point occlusion.
In a monopolar operation, the secondary-lead electrode 35 remains
neutral, while the primary leads 30 are commonly charged and act in
conjunction with an independent electrical device, such as a large
low-impedance return pad (not shown) placed in external contact
with the body, to form RF fields substantially evenly spaced around
the circumference of the vein. The thermal effect produced by those
RF fields along the axial length of the vein wall causes the vein
wall to collapse around the primary-lead electrodes. Upon collapse
of the vein wall, the secondary-lead electrode is charged to have
the same polarity as that of the primary-lead electrodes. The
electrode device is retracted as described in the bipolar
operation.
In either bipolar or monopolar operation the application of RF
energy is substantially symmetrically distributed through the vein
wall. As previously described, the electrodes should be spaced no
more than 4 or 5 millimeters apart along the circumference of the
vein, which defines the target vein diameter for a designed
electrode catheter. Where the electrodes are substantially evenly
spaced in a substantially symmetrical arrangement, and the spacing
between the electrodes is maintained, a symmetrical distribution of
RF energy increases the predictability and uniformity of the
shrinkage and the strength of the occlusion.
As shown in FIG. 14, after the electrodes 34 come into apposition
with the vein wall (FIG. 12), and before the energy is applied to
ligate the vein (FIG. 13), an external tourniquet, such as an
elastic compressive wrap or an inflatable bladder with a window
transparent to ultrasound, is used to compress the anatomy, such as
a leg, surrounding the structure to reduce the diameter of the
vein. Although the compressive force being applied by the
tourniquet may effectively ligate the vein, or otherwise occlude
the vein by flattening the vein, for certain veins, this
compressive force will not fully occlude the vein. A fixed diameter
electrode catheter in this instance would not be effective. The
electrodes 34 which are expanded outward by the formed leads 30 can
accommodate this situation.
The reduction in vein diameter assists in pre-shaping the vein to
prepare the vein to be molded to a ligated state. The use of an
external tourniquet also exsanguinates the vein and blood is forced
away from the treatment site. Coagulation of blood during treatment
can be avoided by this procedure. Energy is applied from the
electrodes to the exsanguinated vein, and the vein is molded to a
sufficiently reduced diameter to achieve ligation. The external
tourniquet can remain in place to facilitate healing.
The catheter can be pulled back during the application of RF energy
to ligate an extensive section of a vein. In doing so, instead of a
single point where the diameter of the vein has been reduced, an
extensive section of the vein has been painted by the RF energy
from the catheter. Retracting the catheter in this manner produces
a lengthy occlusion which is less susceptible to recanalization.
The combined use of the primary and secondary electrodes can
effectively produce a reduced diameter along an extensive length of
the vein. The catheter can be moved while the tourniquet is
compressing the vein, of after the tourniquet is removed.
Where the catheter includes a fluid delivery lumen, fluid can be
delivered to the vein before RF energy is applied to the vein. The
delivered fluid displaces blood from the treatment site to ensure
that blood is not present at the treatment site, even after the
tourniquet compresses the vein.
Where the tourniquet is an inflatable bladder with a window
transparent to ultrasound, an ultrasound transducer is used to
monitor the flattening or reduction of the vein diameter from the
compressive force being applied by the inflating bladder. The
window can be formed from polyurethane, or a stand-off of gel
contained between a polyurethane pouch. A gel can be applied to the
window to facilitate ultrasound imaging of the vein by the
transducer. Ultrasound visualization through the window allows the
operator to locate the desired venous treatment area, and to
determine when the vein has been effectively ligated or occluded.
Ultrasound visualization assists in monitoring any pre-shaping of
the vein in preparation of being molded into a ligated state by the
thermal effect produced by the RF energy from the electrodes.
After completing the procedure for a selected venous section, the
actuator causes the leads 30 to return to the interior of the outer
sheath 12. Once the leads 30 are within the outer sheath 12, the
catheter 10 may be moved to another venous section where the
ligation process is repeated.
The description of the component parts discussed above are for a
catheter to be used in a vein ranging in size from 2 mm (0.08 in)
to 10 mm (0.4 in) in diameter. It is to be understood that these
dimensions do not limit the scope of the invention and are merely
exemplary in nature. The dimensions of the component parts may be
changed to configure a catheter 10 that may used in various-sized
veins or other anatomical structures.
Although described above as positively charged, negatively charged,
or as a positive conductor or negative conductor, these terms are
used for purposes of illustration only. These terms are generally
meant to refer to different electrode potentials and are not meant
to indicate that any particular voltage is positive or negative.
Furthermore, other types of energy such as light energy from fiber
optics can be used to create a thermal effect in the hollow
anatomical structure undergoing treatment.
While several particular forms of the invention have been
illustrated and described, it will be apparent that various
modifications can be made without departing from the spirit and
scope of the invention. Accordingly, it is not intended that the
invention be limited, except as by the appended claims.
* * * * *